Encased and hermetically sealed photocell



Aug. 5, 1952 A. H. AM ENCASED AND HERMETICALLY 'SEALED PHOTOCELL Filed Nov. 26, 1948 Patented Aug. 5, 1952 UNITED STATES PATENT OFFICE ENCASED AND.- HERME'I'ICALLY SEALED PHOTOCELL 4. Claims. (01. 136-89) This invention relates to encased and hermetically sealed photocells, and mor particularly to photocells of the solid disk or. barrier layer type which are hermetically sealed within two-part casings. of which at least the front section is aglass plate. 7

Solid disk phctocells of the current-generating. type are subject to damage from atmospheric moisture. and gases, and this is true of both the selenium and the copper oxide photocells. Various arrangements have been proposed for sealing such photocells within cases. of, or masses of, a transparent organic plastic, and some of the prior proposals have been quite satisfactory within. the limits set. by the characteristics of the transparent plastic material and/or the particular construction of the photocell and its associated terminal assembly.

Objects of the present invention are to provide disk type photocells in sealed casings consisting of or including glass over the photocell for admitting light thereto. Objects are to provide encased photocells in which the glass overlying the photocells maybe colored for a filter action and/or may be so shaped as to limit the angular spread of light rays reaching the photocells. More specifically, objects of the invention are to provide encased photocells in which the casing takes the form of glass plates soldered to each other at low temperatures which do not affect the operating characteristics of the photo'- cells.

These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawings in which:

Figs. 1 and 2 are, respectively, central sections through different forms of glass-encased photocells embodying the invention;

Fig. 3 is a fragmentary side elevation of the Fig... 2 encased photocell, looking towards one of the lead-wires or terminal connections;

Fig. 4 is a plan view, on a smaller scale; of a photocell and its terminal connections:v

Fig. 5 is a fragmentary sectional view showing an. embodiment of the invention for receiving plug-in terminalconnections;

Fig. 6 is a fragmentary sectional view of afiirther embodiment of the invention;

Fig.. 'l is a. fragmentary sectional view, on a 2 smaller scale, of a further embodiment of the invention mounted in an instrument casing; and

Fig. 8 is a side elevation, partly in section, of a photocell casing including a glass cover plate soldered to a metallic rear casing member.

In the drawings, the reference'numeral l identifies a barrier layer type photocell which is encased and hermetically sealed between a cover glass 2 and bottom glass 3. The barrier layer photocell comprises a metal plate or back electrode, a layer of light sensitive material. such as selenium on the back electrode, and a translucent front electrode deposited upon the light sensitive layer in conventional manner. The glass plates 2, 3 are of suiiici'ent' thickness to afford adequate strength for protection of the assembly against mechanical shock and damage during normal handling of the assembly. The glass plates have shallow inturned rims which provide a shallow space or chamber for the reception of the photocell I when the rims are hermetically sealed to each other. The rims may be directly fused to each other without raising the photocell to destructive temperatures when the casing plates are of so-called oven-glass. Ordinary glass and conventional glass working techniques can not be employed but the central portions of glass plates 2, 3' of oven glass can be sharply chilled by an air blast to protect the photocell during the fusion and hermetic sealing of the rims to each other.

The terminal or lead-in Wires 4, 4 of the photocell are arranged between the rims before they are fused and united, thereby sealing the lead-in wires in the glass wall of the casing.

The photocell may be of any desired shape and size but preferably is a circular disk, as shown in Fig. 4, with a pick-up electrode 5 in the form of one or more small spots of a low melting point alloy sprayed upon the outer electrode layer of the photocell. A- line lead wire 6 is soldered or welded to the pick-up spot or spots and to the inner end of the lead-in wire 4'. The advantage of small pick-up spots over the conventional annular collector rings isthat the active light sensitive area of a photocell is'thereby increased by as much as about 25%. The pick-up spot 5 may be very minute, for example of the order of 0.05 diameter, and the lead wire 6 is a fine fila-- mentary conductor which shades. only a neglfgfble portion of the photocell surface. The lead-in wire 4 is soldered or welded to the back electrode of the photocell The photocell is spaced from the back cover and pressed into contact with the inner surface of the cover glass 2 by any appropriate means such as a spring, a resilient washer or, as illustrated, by lugs or projections at the inner surface of the back cover glass 3. The outer electrode surface of the photocell is thereby positioned substantially parallel to, and in contact with or in close proximity to, the inner surface of the cover glass 2.

As shown in Figs. 2 and 3, the casing may be formed by glass plates 2a, 3a having rims -with mating surfaces which are metallized and united by solder 8, the solder having a melting point below the critical temperature which will damage the photocell. tend through and are sealed in glass insulating sleeves 9 having a metallized outer surface 8, and the rims of the glass plates 2a, So have complementary semi-cylindrical grooves Hi, see Fig. 3, for receiving the insulating sleeves. The metallized surfaces of the sleeves unite with the adjacent metallized surfaces of the glass plates to completethe hermetic sealing of the photocell casing.

As shown in Fig. 5, glass sleeves i2 which are externally metallized and soldered between the glass casing plates 2a, 3a may be tubular and provided with internal metal'coatings Hi to which lead wires M from the encased photocell, not shown,,are connected by solder l5 which seals off the inner ends of the bores of the tubular glass sleeves l2. The metallized surface |3 of sleeve |2 forms a socket for receiving a pin type connector l6 of an external circuit lead IT.

The terminal pin-and-socket connection may be reversed, as shown in Fig. 6, to locate the pin elements on the sealed photocell assembly. Tubular pins IS with small openings in their outer rounded ends are sealed within glass bushings I?! by solder 20, the bushings passing through openings in the rear casing plate 3 and being sealed by solder 2| to locally metallized surfaces at the interior of the casing plate 3. The photocell terminal wires 22, 23 are drawn through the tubular pins I8 and electrically connected thereto bysolder24 which seals the ends of the pins I8. The projecting ends of the terminal wires 22, 23 arethen cut off. As shown in Fig. 6, the terminal connector 23 extends through a small central aperture in the photocell and may be a stranded conductor with the individual conductors bent over and welded or soldered to different points along a small annular pick-up electrode 25, as describedand claimed in my prior Patent No. 2,403,863, granted July 6, 1946'. A resilient washer 1' may be arranged beneath the photocell I' to maintain the latter in contact with the cover glass when the housing is assembled and sealed.

The location of the photocell terminals on the rear casing member is particularly advantageous, whether the terminals be conductors, pin sockets or pins, since this construction facilitates the assembly of an encased photocell in photoelectric measuring instruments, for example light meters and. exposure meters. A plug-in encased photocell may be mounted in or assembled as a unit of a photoelectric measuring instrument, as shown in Fig. 7, by introducing the encased photocell into a recess in an insulating casing member 26 of the instrument to insert terminal pins |8 in sockets 2.1 molded in the member 26.

The lead-in wires l, 4 ex- I Omitted;

Terminal lugs 28 are secured to the sockets 21 for establishing the desired circuit connections between the photocell and the measuring instrument, not shown. A metal plate 29 of the instrument casing extends over a radial shoulder of the outer glass plate 2 to retain the photocell casing in the recess of the base 26. As shown, the cover glass 2 has an outer lenticular surface 30, and a mechanical bailie 3| is molded into the plate 2' to cooperate with the lens surface 30 to limit the angular spread of the light rays which can reach the photocell.

, The cover glass of the photocell casing may be tinted to serve as a filter for the photocell and, for measurement of incident light intensity, the bafile 3| and the outer lenticular surface may be It will be apparent that the back plate 3b of the photocell housing may be of metal, as shown in Fig. 8, with a flanged rim to which the metallized rim of the cover glass 2a is soldered. The details of the photocell and its connections are not illustrated in Fig. 8 since, except for the substitutionof the metal back plate, the assembly may be substantially as illustrated in Figs. 2 and .3.

The space within the casing may be exhausted, or may be filled with dry air or with a dry inert gas. The hollow pin terminals l8 of the encased photocell of Fig. 6 afford a convenient means for introducing a moisture-free gas or air into the casing after the rims of are soldered to each other. The dry gas or air is forced into one hollow terminal I8 to displace casing. The ends of the leads 22, 23 are then soldered to the the air already present within the terminals |8 to complete the sealing of the casing. Although it is presently preferred to form the sealed photocell housing from two complementary the invention as set forth in the following claims.

I claim:

1. An encased and hermetically sealed photocell as sealed in claim 2, wherein the rear member is dished and of metal.

2. An encased and hermetically sealed photo cell of the barnier layer casing member of glass with a metallized rim, a back casing member soldered to the metallized rim of said front glass casing member, a selenium barrier layer photocell between said casing members, insulating sleeves extending between'and having outer metallized surfaces solder sealed to the respective casing members, and terminal wires for said photocell extending into and sealed in said insulating sleeves.

3. An encased and hermetically sealed photocell as recited in claim 2, wherein said terminal wires extend through and are sealed in said insulating sleeves. v

4. An encased and hermetically sealed photocell as recited in claim 2, wherein said insulating sleeves are tubular and have metallic coatings on and said terminal wires extend into the inner ends-of said tubular sockets and are electrically the glass plates 2' and 3 casing type comprising a front connected to said metallic coatings by solder which seals the bores of said tubular insulating sleeves.

ANTHONY H. LAMB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,697,451 Baird Jan. 1, 1929 2,067,843 Tonnies Jan. 12, 1937 2,097,073 Long Oct. 26, 1937 Number Number 10 777,941

Name Date Treacy Dec. 20, 1938 Ziengenbein Dec. 27, 1938 Touceda et a1 Nov. 26, 1940 Wrobel Feb. 25, 1947 Bierwirth June 8, 1948 FOREIGN PATENTS Country Date France Mar. 5, 1935 OTHER REFERENCES Welo, Journal Optical Society of America, volume 8 (1924) page 453. 

